Recently, people, especially the middle-aged and senior, are becoming health-conscious, as typically seen in frequent appearances of the word “metabolic syndrome” on newspapers, and accordingly, actively take exercises such as jogging and exercises using a training device such as a bicycle ergometer. It is said that one needs to pay sufficient attention to his physical condition when taking such an exercise. For example, it is said to be good to monitor an exercise load by checking pulse etc. so as to prevent excessive exercise.
Against this backdrop, a pulse meter which makes it possible to easily take one's own pulse anywhere and anytime is sought after, and accordingly, portable pulse meters have been proposed. There are various types of pulse meters. Recently-proposed one is a pulse meter in which a pulse sensor is realized by a photointerrupter which emits and receives infrared rays or the like. Such a pulse meter is used as a small portable pulse meter.
Patent literature 1 discloses a bioelectric impedance measurement device which has a photointerrupter so as to additionally measure a pulse rate.
FIG. 24 is a schematic view illustrating the bioelectric impedance measurement device. In FIG. 24, 245 indicates a main body 245 of the bioelectric impedance measurement device. A surface of the main body 245 is provided with (i) a display section 246, (ii) an electrode group 247 which is made up of a plurality of electrodes, and (iii) a sensor 248 which is known as a reflective photointerrupter and into which a light-emitting element and a light-receiving element are incorporated.
The bioelectric impedance measurement device allows a user to know his body fat by touching the electrode group 247 with his fingertip or the like so that his bioimpedance is measured. Further, the sensor 248 of the bioelectric impedance measurement device makes it possible to measure a pulse rate. The following shows only a simple overview of how to measure a pulse rate by using a photointerrupter. Since it is already known how the pulse rate is measured by a photointerrupter, details thereof are omitted in the following.
First, a test subject touches the sensor 248 with his fingertip. Then, the light-emitting element generates infrared rays so as to irradiate a blood vessel of the fingertip with the infrared rays. Then, the light-receiving element receives light reflected from the blood vessel so as to detect a change in blood flow volume inside the blood vessel which change is caused in accordance with a heartbeat. A pulse rate is calculated on the basis of the detected results. In actual measurement, the test subject keeps touching the sensor 248 with his fingertip for a certain time.
Patent Literature 2 discloses an optical pulse sensor which is provided to an exercise machine such as a bicycle ergometer. FIG. 25 is a view illustrating the pulse sensor which is worn by pinching an earlobe. In FIG. 25, 250 indicates pinching members for pinching an earlobe therebetween. A sensor 251 is provided to tip sections of the pinching members. The sensor 251 is realized by a photointerrupter made up of a light-emitting element and a light-receiving element. In this example, a transmissive photointerrupter is adopted as the sensor 251. However, the pulse sensor operates, as a pulse meter, on the same operating principle as the art disclosed in Patent Literature 1. The sensor 251 is connected with a cord 252. An output of the sensor 251 is supplied to a main body (not illustrated) via the cord 252. The main body calculates a pulse rate on the basis of the output from the sensor 251 so as to display the calculation result on a display apparatus (not illustrated).